Fundamentals of structure-property relationships in blown films of linear low density polyethylene/low density polyethylene blends

This study was undertaken to fundamentally understand structure-property relationship of blown films of linear low density polyethylene/low density polyethylene blends over the entire composition range via decoupling orientation effects from their intrinsic properties. Three different low density polyethylene blends with an octene Ziegler-Natta linear low density polyethylene resin were studied. The machine direction tear strengths of blown film of linear low density polyethylene/low density polyethylene blends went through a minimum as the low density polyethylene concentration increased, almost a mirror image of the melt strength curve for these blends. The machine direction tear decreased significantly up to 40% low density polyethylene, much sharper decrease compared to decrease in intrinsic tear suggesting orientation effects dominating the machine direction tear behavior. The decrease in the dart impact and puncture energy was also due to both an increase in the machine direction orientation, and a decrease in the intrinsic toughness due to decrease in the tie chain concentration, as the low density polyethylene content increased.